The present invention relates to water heaters, water heater flues and heat exchange elements which are or can be installed in flues of water heater systems.
Prior art heat exchangers for hot water heaters generally comprise individual fins or vanes welded in predetermined patterns on the flue, so that air passing through the flue will be caused to flow in a spiral fashion. The fins or vanes also act as heat exchange elements which help to conduct heat to the flue wall and thus to the water contained in the vessel through which the flue passes.
In Australian patent application 18306/76 published on Apr. 13, 1978 there was described a series of individual vanes placed in helical fashion around the circumference of a flue and angled to the longitudinal direction of the flue so as to produce a swirling effect. Each vane was individually welded to the flue.
U.S. Pat. No. 2,950,740 which issued on Aug. 30, 1960, describes a similar arrangement to that described in the Australian patent application 18306/76. Whereas U.S. Pat. No. 3,349,754 which issued on Oct. 31, 1967 discloses a modified construction to that of U.S. Pat. No. 2,950,740, but modified by the individual vanes terminating at a central core region of the flue. Each of the above US patents, like the Australian reference, discloses individually located and welded vanes or fins. These vanes or fins arm relatively time-consuming to install if welded to the flue manually. Otherwise, to weld by machine requires complicated and expensive machinery.
Another difficulty with prior art constructions is that those fins closest to the combustion chamber tend to oxidise and progressively disintegrate. This can occur because of the damage caused by the absorption of excessive heat.
Corrosion can also occur in the fins elsewhere along the flue, if the flue is relatively efficient in extracting heat form the exhaust gases. This is particularly the case at the downstreams portions of the flue, because by the time the gases reach these portions, the temperature of the exhaust gases can drop below the dew point of the moisture contained in the gases. This will result in deposition of moisture on the downstream portions of the flue. If moisture builds up sufficiently and if combustion in the combustion chamber is switched off (such as when the water reaches the desired temperature), then the moisture can spread or drip to other portions of the flue causing erosion and creating a relatively hostile environment for the flue and fins.
One common solution to this moisture, corrosion and hostile environment is to enamel the interior of the flue. However, with individual fins being welded to flues, this is generally not done, because of difficulties in attempting to enamel fins having sharp edges and the like. In such situations it has been found that enamel does not stick the fins. If they are enamelled, because the enamel may only temporarily stick to the metal, and because of the hostile environment at the upstream end of the flue, the excessive heat will cause the enamel linings to disintegrate. Once this disintegration of the enamel occurs, corrosion or oxidation starts in the fins or vanes, which can then continue into other areas, accelerating the deterioration of the flue system, and thus the water heater.
The present invention provides a heat exchange element adapted to be attached to a surface of a flue of a water heater, and having an imaginary X axis along its length and an imaginary Y axis across its width being orthogonal to said X axis, and an imaginary Z axis orthogonal to the X and Y axes; said Z axis having a positive and negative direction, said negative direction beginning at, and extending away from a rear surface and said positive direction beginning at, and extending away from a front surface; a support member extending in the X axis direction having at least one vane on each of two opposing sides of said support member, said vanes being spaced apart in the Y direction on the supporting member; said vanes extending generally away from said front surface in a direction having a positive Z direction component.
The present invention also provides a heat exchange element adapted to be attached to an inside surface of a flue of a water heater, and having an imaginary X axis along its length and an imaginary Y axis across its width orthogonal to said X axis and an Z axis orthogonal to the X and Y axes; said Z axis having a positive and negative direction, said negative direction beginning at, and extending away from a rear surface and, said positive direction beginning at, and extending away from a front surface; a support member extending in the X axis direction having at least one vane extending in a direction having a positive Z direction component away from said front surface and on at least one side of said support member, wherein said support member is of a length greater than the extent of said at least one vane from said support
The present invention provides a heat exchange element including:
an elongate base portion, having front and rear longitudinally extending surfaces, the rear surface being of a profile to substantially match a surface of flue to which said element is to be attached;
a plurality of vanes arranged along the base portion and projecting forwardly relatively to said front surface, said element having an imaginary X axis along its length and an imaginary Y axis across its width, said Y axis being orthogonal to said X axis, and an imaginary Z axis orthogonal to the X and Y axes; said Z axis having a positive and negative direction, said negative direction beginning at, and extending away from the rear surface and said positive direction beginning at, and extending away from the front surface.
Preferably said element is formed from a sheet material and is folded into a desired shape.
Preferably said element is formed from a channel member.
Preferably said element is formed from a substantially L-shaped member.
Preferably said element is constructed so that the X axis is positionable substantially parallel to a longitudinal axis of a flue.
Preferably each vane is an elongated tab or finger like projection.
Preferably at least one vane is oriented at an angle in the range of 0xc2x0 to 35xc2x0 to said X axis.
Preferably there is located one vane only on each of two opposing sides of said element parallel to said X axis, each vane extending parallel to said X-axis and being of substantially the same length as said support member.
Preferably said element is constructed so that when said X axis is positioned substantially parallel to said longitudinal axis of said flue, said vane means is at substantially the same angle to said longitudinal axis of said flue as it is to said X axis.
Preferably said rear surface includes a contour which substantially matches the contour of a surface of a flue to which it is to be attached.
Preferably said contour renders said element positionable relative to said flue, so that said X axis is only positionable substantially parallel to said longitudinal axis of said flue.
Preferably said rear surface includes a shape which provides at least one band, extending parallel to said X axis, by means of which said element can contact and be attached to said inside surface of said flue.
Preferably said rear surface includes, about said X axis, an external radius, not larger than an inside radius of said flue, said external radius being adapted to be connected to said inside surface of said flue.
Preferably said rear surface of said support member has a contour, shape or radius which provides said rear surface with a concave or convex shape relative to said negative direction of said Z axis.
Preferably at one end of said element said vane or vanes terminate at a lesser distance from said support member than the vanes or a portion of the vane, at the second end of said element.
Preferably at one end of said element said vanes have the same length for a predetermined length of said element, whereupon the length of said vanes progressively decreases so that at another end the length from said support member of said vanes is the shortest length of the said vanes on said element.
Preferably said predetermined distance is in the range of 50% to 80% of the length of said element.
Preferably said support member is generally planar except for a contour on the rear face of said support member.
Preferably said vane or vanes are generally planar.
Preferably said vane or vanes is part helical.
Preferably said vane or vanes imparts a motion which is at least part helical, to gases flowing over them.
Preferably said vane means extend from two sides of said support member.
Preferably on one side or both sides of said support member there is a plurality of vanes.
Preferably said vanes are formed initially at an obtuse or acute angle to said Y axis on said support member prior to being folded or bent into a desired shape.
Preferably each vane or groups of vanes are at an angle to the X axis which is different from each other vane or other groups of vanes.
Preferably vanes or groups of vanes at one end of said element are at no, or the smallest angle to said X axis by comparison to the angle to said X axis of a vane at the other end of said element.
Preferably each subsequent vane along the length of the element is at a progressively larger angle to the X axis by comparison to said smallest angle.
Preferably gaps or spaces between adjacent vanes or in groups of adjacent vanes, are of a substantially constant dimension.
Preferably gaps or spaces bent adjacent vanes or in adjacent groups of vanes decreases from a maximum to a minimum from one end of said element to the other.
Preferably an end of said element to be positioned in an end of said flue which is nearest to a combustion chamber of a water heater, has one of, or a combination of two or more of the following: a larger gap or space between adjacent vanes than other gaps or spaces between adjacent vanes; a larger gap or space between adjacent vanes in a group of vanes than other gaps or spaces between adjacent vanes in adjacent groups of vanes; vanes with the smallest angle to the X axis by comparison to the angle of other vanes; the group of vanes with the smallest angle to the X axis by comparison to the angle of other groups or another group of vanes, the shortest vane by comparison to the length of other vanes; the group of shortest vanes by comparison to the length of another group or other groups of vanes; the narrowest vane by comparison to the width of other vanes; the group of narrowest vanes by comparison to the width of another group or other groups of vanes.
Preferably said heat exchange element is secured to a flue of a fire water heater.
Preferably said heat exchange element is coated with enamel after it is installed in said flue.
The invention also provides a fired water heater including a heat exchange element as described in any of the above paragraphs, located in a flue of said water heater.
Preferably the fired water healer includes a baffle is located said flue at an upstream end thereof, to direct exhaust gases through said beat exchange elements.
Preferably said baffle includes a cylinder closed at one end.
Preferably said baffle includes a flange at one end of said cylinder to support said end of said cylinder from the vane or vanes of said heat exchange element, with said cylinder extending in an upstream direction from the downstream-most end of said heat exchange element.
The invention further provides a method of manufacturing a heat exchange element, said method including the step of: selecting or forming a generally planar elongate piece of sheet metal having an imaginary X axis along its length and an imaginary orthogonal Y axis along its width and an imaginary Z axis orthogonal to said X and said Y axis, said Z axis having a positive direction beginning at and extending from a front face of said sheet, and a negative direction beginning at and extending from a rear face of said sheet; and:
(a) forming at least two vanes connected to and extending away from at least one side of a central portion of said element, or on opposite sides of a central portion of said element, said central portion forming a support member, said vanes being separated from each other by a space; and
(b) rotating said vanes relative to said support member so that each of said vanes has a positive Z axis direction component.
Preferably said vanes is a series of individual finger like vanes.
Preferably all of said vanes at least on one side of said support member are rotated to the same angle to the X axis.
Preferably all of said vanes, on one side of said support member are rotated to the same angle to the Y axis.
Preferably all of said vanes at least on one side of said support member are rotated to the same angle to the Z axis.
Preferably the method at step (b) also includes forming said vanes of a shorter length at one end of the length of said support member than the vanes at the other end of said support member.
Preferably vanes are formed on two sides of said support member and are a directed away from said support member so as to have at last some component of their direction in the positive direction of the Z axis.
Preferably all vanes on one side of said support member are substantially parallel to each other, when viewed from 2 orthogonal directions.
Preferably after said final step, said vanes are in an orientation such that each adjacent vane is either substantially collinear or parallel to each other vane along one side of said support member.
Preferably said support member is welded along its length to a flue for attachment to a fired water heater.
Preferably said steps of said method are formed by means of stamping and or pressing and or rolling processes, and or laser cutting.
The invention also provides a beat exchanger assembly including:
a tubular flue having an internal surface or surfaces about a passageway for gas flow; and
a plurality of heat exchange elements spaced about the axis of the flue and fixed to said internal surface(s) so as to lie in said passage way;
wherein each of said beat exchange elements is elongate in a direction along the flue, has a base portion relatively wider than it is thicker adjacent to a complementary portion of said internal surface for transferring beat to the flue, and further having a vane or vanes arranged along the base portion and projecting from the base portion into the passage way.
Preferably said vane is a tab or/finger or said vanes are a plurality of similarly shaped tabs or fingers.
Preferably said tabs or fingers are spaced apart less than their width.
Preferably said tabs or fingers are in pairs with each pair being either convergent forwardly of divergent forwardly from the base portion.
Preferably said base portion has a rear face which is profiled or arcuate in transverse cross section, with vanes extending along radii of a circle which is defined by the inside diameter of said flue.
Preferably said vanes each include a portion which is a generally rectangular flat tab.
Preferably said tabs or fingers are in off-set parallel planes.
Preferably said tabs or fingers are at a predetermined angle to a plane bisecting the base portion along its longitudinal axis.
Preferably a baffle is located in said flue at an upstream end thereof, to direct exhaust gases through said heat exchange elements.
Preferably said baffle includes a cylinder closed at one end.
Preferably said baffle includes a flange at one end of said cylinder to support said end of said cylinder from the vane or vanes of said heat exchange element, with said cylinder extending in an upstream direction from the downstream-most end of said heat exchange element.
The invention further provides a water heater having a heat exchange assembly as described in any of the above paragraphs.
The advantage of the method embodiment of the invention is that a relatively quick and efficient method of manufacturing the vanes of a heat exchange element is provided. An advantage of the other embodiments is the provision of a surface for contacting the surface of a flue, which will produce a relatively high level of heat transfer to the flue to which the heat exchange element is connected, compared to other methods of contacting the two components, said element is constructed so that when said X axis is positioned substantially parallel to said longitudinal axis of said flue, said vane means is at substantially the same angle to said longitudinal axis of said flue as it is to said X axis.